The long-term studies of natural formations in the optical wavelength range are described. The results of development and the creation of devices and ground-based, air-and spaceborne videospectral systems for study of the earth's surface by spectral methods, laboratory and flight equipment adjustment are considered.

No abstract

<p>Forests play an important role in global carbon, hydrological and atmospheric cycles. Current environmental issues have a strong impact on forest health. Satellite remote sensing is widely used for forest state monitoring due to increasing availability of satellite data and high temporal resolution. However, a spatial resolution of satellite data is often insufficient to detect small areas of forest drying. For a clearer detection of affected forest areas, spectral unmixing is required.</p> <p>The results of spectral unmixing of Belarusian spacecraft data (4 bands: blue, green, red, NIR; spatial resolution 10 meters) are performed. To detect affected forest areas that need to be specified, the vegetation index NDVI is calculated. Then, spectral mixture analysis is running for these areas. The library of endmembers (pure spectral signatures) was created by ground measurements using spectral instruments that were developed in the department of aerospace researches of Belarusian state university. Comparison of spectral unmixing results and airborne measurements shows high agreement. Airborne measurements of study forest area was carried out using Leica airborne digital sensor. Spatial resolution of airborne data is around 40 centimeters. The developed spectral unmixing approach can be used for other tasks, such as burned area mapping, crop monitoring, etc.</p>

The videospectral system (VSS) intended for ecological space experiment on board of the International Space Station (ISS) has been developed by the Aerospace Researches Department of the Institute of Applied Physical Problems of the Belarusian State University. The system comprises three matrix spectrometers MP-15. The polychromator of each spectrometer includes the imaging fiber, the entrance slit, concave holographic diffraction grating, and a CCD array detector. The array photodetector measures the spectral radiation distribution in rows, and the spatial distribution (image) in columns.Astigmatism is a typical aberration of polychromators based on concave spherical gratings -rays in tangential and sagittal planes are focused at different points. This degrades as for spectral and spatial resolution along the entrance slit.The proposed method of obtaining high spatial resolution without spectral resolution loss consists in the displacement of the output end of the imaging fiber along the optical axis at a specified distance from the entrance slit. After that the rays in the tangential and sagittal planes focus at one point. The entrance slit operates as a one-dimensional aperture to obtain high spectral resolution.

Onboard the International Space Station (ISS), as a part of the “Uragan” Earth exploration experiment, various observation devices are used, including photo and video spectral equipment, the orientation of which is carried out manually by the crew through the portholes. However, severe limitations are imposed on the planning of such experiments, primary related to the necessity taking into account the crew’s daily routine and the availability of time allocated for scientific experiments. The solution for expanding the ability to conduct experiments is the employing of automated orientation platforms (OP). One of these OPs is the video spectral equipment orientation system SOVA-1-426. A method for orientation angles forecasting of optical instruments for pointing at predefined objects on the Earth’s surface with SOVA-1-426 is presented. Moreover, in the described method, in addition to the coordinates of the center of mass, the current orientation of the ISS is taken into account, which makes it possible to perform the forecast with better precision. Taking into account the ISS orientation is carried out through the use of the ISS rotation quaternion to control the platform in automatic mode. The presented method for the orientation angles forecasting of high-resolution photo-camera aboard the ISS by employing SOVA-1-426 allows its automatic alignment on the Earth’s surface objects with accuracy up to seven kilometers. The described method is implemented in software and is currently used in the SOVA-1-426 OP aboard the ISS for the remote sensing of the Earth’s surface.